In 1814, when Mary was seventeen years old, she started a relationship with Percy, who was married at the time. Percy and Mary started secretly meeting each other at her mother's grave. When Godwin found out he tried to end their relationship, but did not succeed.
They left for France with Mary’s stepsister and only returned when they had no money left. When they arrived back Mary was pregnant and her father refused to help.
“Percy was constantly leaving home, escaping from creditors and also at the time Percy's wife gave birth to their son and Percy seemed to want Mary Shelley to have an affair with his friend
Hogg.” (egs.edu) They went to Geneva in 1816 with Claire Claremont to spend the summer with Lord Byron who Claire was having an affair with at the time. They spent the majority of their time indoors because of the bad weather. They spent a good bit of their time talking about galvanism and telling ghost stories. This helped write her rough draft of what would be her most famous novel Frankenstein: or The Modern Prometheus. Soon after they returned from England Percy’s wife who was Mary’s sister committed suicide. Percy’s lawyer told him to marry Mary, and he did at the end of